Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $77.74   10.364%   $85.797   $85.80   $85.80   $85.80  
  Purchase #2 $124.84   8.682%   $135.6786   $135.68   $135.70   $135.70  
  Purchase #3 $101.91   8.685%   $110.7609   $110.76   $110.75   $110.80  
  Purchase #4 $113.87   4.573%   $119.0773   $119.08   $119.10   $119.10  
  Purchase #5 $175.42   3.374%   $181.3387   $181.34   $181.35   $181.30  
  Purchase #6 $238.95   10.551%   $264.1616   $264.16   $264.15   $264.20  
  Purchase #7 $129.87   3.851%   $134.8713   $134.87   $134.85   $134.90  
  7 purchase totals = $962.60       $1,031.6854   $1,031.69   $1,031.70   $1,031.80